1. Field
This invention relates to devices that communicate over fiber optic waveguides. More particularly, it relates to the realization of optical time domain reflectometer (OTDR) functionality within such devices.
2. Background
Fiber optics offers high data rate, low weight and electromagnetic interference immunity for data communications, making it suitable for use in modern aircraft, helicopters, unmanned avionic vehicles, space-craft and missiles. These platforms require sensor and control data to be distributed throughout the system. Fiber optic components must be able to operate and survive in this environment. Fiber optic components must be made in compact packages to fit within strictly defined physical envelopes.
Fiber optic components in this environment may become damaged. Component can be constructed with a ‘fixed pigtail’, a short run of fiber that is permanently attached to the component. Often, components designed for harsh environments have a fixed pigtail that passes through a hermetically sealed can. The electronic and optoelectronic (OE) devices (e.g., PIN detectors, lasers, and LEDs) are contained inside the sealed can.
The process of making a hermetic pass-thru of the fiber is expensive, consumes considerable package volume, and is not compatible with re-work. Some fiber components use a ribbon made up of multiple fibers (typically 12). The process sealing the ribbon fiber feed-thru is much more difficult and expensive than a single fiber.
Also, optical fiber optic connectors are typically not compatible with a solder reflow process. Therefore, if another component on a printed wiring board needs to be replaced, the fiber optic component must be removed prior to solder re-work. This additional handling of the fiber optic component also exposes the fiber pigtail to damage.
Further, maintaining the alignment of OE devices, lenses and the optical fiber in a non-temperature controlled environment is challenging. The OE devices are typically formed in an III-V material with a coefficient of thermal expansion (CTE) below 6 ppm/C, while the lenses that couple light between the OE devices and fibers are typically molded in a plastic material with a CTE above 30 ppm/C. This large difference in CTE causes issues of maintaining alignment over temperature.
Accordingly, there are multiple areas of difficulty in the fiber optical component industry. In view of above and other challenges in the industry, methods and systems are described below that provide, among other things, precision alignment, low-cost fiber optic modules, an optical path that can be sealed from contamination, and a pigtail that can be connectorized or replaced with a simple process.